Recently, especially in the context of the so-called “smart metering” application, public or private utility companies have started to deploy their own communication networks. These networks (referred to as sensor networks in the following) may, for example, connect commercial end users to the different levels of voltage transformer stations. These may be low voltage, medium voltage or high voltage transformers or even the respective energy dispatch center. To a wide extent, optical fiber infrastructure will be used for these communication networks. The whole network setup and hierarchy is quite similar to a telecommunication application. However, the actual bandwidth demand per end customer is significantly lower. In particular, the network area on the level of low voltage transformers is different to a telecommunication company's transmission network, especially with respect to the bandwidth required and desired network topology. Typically, a data transmission rate of a few Mbit/s per low voltage transformer node will be sufficient, and relatively large sub-network domains of up to 100 nodes in a linear bus geometry may be advantageous as a physical network topology. Of course, also a sufficiently high availability of the required network connections including fiber protection is desirable.
As a linear bus geometry or a physical linear bus architecture, respectively, is desirable, a classic time division multiplex (TDM) network, for example a network according to the synchronous optical network (SONET) standard or the newer synchronous digital hierarchy (SDH) standard, could be chosen for this data transmission application. A TDM network would meet the requirements as to data transmission rate and the network nodes with their East/West interface structure would easily enable to realize the bus structure. However, as such a sensor network should be realizable and maintainable at acceptably low costs, the classic TDM structure (SONET/SDH) and the known structures for suitable network nodes are too complex and too expensive. Especially, providing separate interfaces for the eastern and western ports of a remote node suitable for such linear TDM structures lead to inacceptably high costs.